Conventionally, in the medical field, endoscopes are used, for example, by inserting an elongated insertion portion into a body cavity to observe an organ in the body cavity, for example, a large intestine, or to perform various treatments using a treatment instrument which is inserted into a treatment instrument insertion channel if necessary.
When the insertion portion of the endoscope is inserted into the body cavity, a user, who is an operator, grasps a flexible tube portion (flexible portion) and, while pushing the portion into the body cavity, bends an bending portion (angle portion) in a desired direction by performing a predetermined operation of an operation knob which is provided in an operation portion of the endoscope.
For example, in Japanese Unexamined Patent Application Publication No. 5-31065, an insertion portion of an endoscope is proposed. In the endoscope insertion portion, in order from a distal end, a distal end rigid portion, an angle portion, and a flexible portion are provided. In the endoscope, spiral pipes provided the inside and outside of the insertion portion are spot-welded at predetermined pitch intervals in the axis line direction. In the endoscope, the spot-welded portions become joints and become hard due to increased resistance against the bending. Further, the endoscope has a characteristic structure that as the welding pitch intervals become narrow, the hardness increases.
Further, in the endoscope, at a root side of the insertion portion, that is, at a connection side to a main body operation portion, the welding pitch intervals become short, and at a distal end side, that is, at a connection side to the angle portion, the welding pitch intervals are varied to be wide in order to substantially continuously vary the hardness from the root side to the distal end side of the insertion portion.
When the insertion portion of the endoscope described in the above-described Japanese Unexamined Patent Application Publication No. 5-31065 passes through a bending portion in the body cavity, the flexible portion is bent while following along the body cavity wall.
However, the angle portion of the endoscope becomes a bending state greater than the bending state of the flexible portion having a predetermined hardness depending on the bending degree of the operation. That is, independently of the bending state of the body cavity or the bending state, the bending portion locally becomes a large bending state against the flexible portion in response to the bending operation of the operator.
The bending portion being in the bending state, according to the force quantity pressed by the user, presses the bending body cavity wall, and further, rapidly bends the body cavity. Then, the bending portion is hooked at the rapidly bent body cavity wall. Accordingly, the body cavity is heavily burdened and is drawn more than necessary. As a result, the patient is largely burdened at the endoscopy, and is distressed.
Accordingly, the present invention has been made in view of the above, and an object is to provide an endoscope which suppresses resistance occurs when the bending portion passes through the bending portion of the body cavity at the endoscopic inspection and increase insertion performance of the insertion portion to reduce the burden and pain to patients.